Or just direct them to the forums where they can get more personalised advice for factions that you aren't familiar enough with to offer them advice for. Although I understand that there's pitfalls to this approach: forumites will inevitably suggest the entire faction roster as a starting point as each member chimes in with his own personal favourites, the forums might be more competitively oriented than you are guiding your local group to be, etc.
I think the faction forums right here are actually quite good in that respect, they are not that populated and the people that would tunnel newbies into a certain play style generally don't care enough to reply. I can't speak for everyone, but in Cryx, when somebody comes in and asks for advice, we try to ask for their preferences and what they have available and guide them from there. Maybe I'm biased, but I would like to say we're doing an ok job there.
elshinare Good idea to go over the themes. So in addition to my earlier advice of getting some staples like Stalkers, Nightwretches, Machine Wraiths and Overlords, I would suggest the following:
Infernal Machines, the steam-powered zombie theme, not recommended, because it's not the best, but can be fun:
Mechanithrall boat + Necrosurgeon, Warwitch Siren, Pistol Wraith, Hellslinger Phantom (Machine Wraiths fit here)
The Ghost Fleet, the zombie pirate/Pirates of the Caribbean theme, not recommended because it's very linear and doesn't "tick" until you basically fill out 75 points:
full unit of Revenant Crew + WA, Rengrave, Hellslinger Phantom. Later add Blackbane's Ghost Raiders and Agrimony.
Black Industries, the jack theme:
Deathjack, Warwitch Siren, Black Ogrun Ironmongers, Aiakos1, add jacks to taste (Overlords and Machine Wraiths fit here very well)
Scourge of the Broken Coast, the horny chick (pirate) theme:
Satyxis Raiders, Satyxis Gunslingers, Axiara, Severa, Satyxis Blood Priestess, Misery Cages
Slaughter Fleet Raiders, the living maniacs/pirate theme:
Actually might want to go with the box here, it's great value and gives you a great start. Otherwise, go with Bloodgorgers + Jussika + Gerlak, Misery Cages, Black Ogrun Smog Belchers
Dark Host, the slow moving undead that hit like a ton of bricks theme:
Full unit of Bane Warriors + CA, Tartarus, a Wraith Engine.
Recommended beginner casters, not too hard to learn and can give some insight into the rest of the faction and/or look cool:
Agathia: wouldn't play her in IM, and is not a great fit in BI, but can do the others well enough.
Terminus: fits into DH, GF and IM
Deneghra 1: just plug her into anything that's not BI
Asphyxious 1: fits into anything that has infantry that doesn't need too much help with hitting, so just don't put him into IM or BI (he can work there, but with more specific builds)
Skarre 1: can fit anywhere really. I suppose her least favourite theme would be Infernal Machines.